1. Field of the Invention
The present invention generally relates to information processing, particularly to document processing and more particularly to a document tagging method and apparatus.
2. Description of Related Art
In the age of Internet, a large amount of information over the Internet greatly facilitates knowledge of people about information on various aspects, including opinions on various entities of interest, referred to as focused entities (“entity” in this application includes a subject which is an object or an event). For example, an opinion on an entity includes a positive opinion, a negative opinion, etc. An attribute of whether an opinion is positive or negative is referred to as a “sentiment polarity”. A technology of deriving a sentiment polarity on an entity is referred to as a sentiment analysis technology. Currently, there are various sentiment analysis technologies available. For example, US 2009193328 describes an “Aspect-Based Sentiment Summarization,” US 20080154883 describes a “System and Method for Evaluating Sentiment,” US 20050125216 describes a method of “Extracting and Grouping Opinions from Text Documents,” WO 2008083504 describes a “Method and System for Information Discovery and Text Analysis,” US 20090048823 describes a “System and Methods for Opinion Mining,” and US 20080133488 describes a “Method and System for Analyzing User-Generated Content.”
However, in analyzing a sentiment on specific contents (a keyword, an entity, etc.), only a fragmentary knowledge about the polarity of the sentiment is derived. Thus, such analysis obstructs people from getting a full insight of an article or a subject. Particularly, since respective entities and thus opinions on them are isolated, it is impossible to reflect the relationship among the respective entities. Furthermore, an entity and a source from which the entity is fetched (e.g., a document, etc.) are isolated, while in fact, associations between entities and between an entity and its source are important in gaining helpful information.